The present disclosure relates generally to methods and apparatus for forming a transmission assembly for a downhole motor; and more specifically relates to methods and apparatus for coupling components in the transmission assembly together in a manner which assists in the transmission assembly having capability of communicating high torque loads as may be experienced in some drilling operations.
The use of positive displacement-type mud motors in downhole operations presents significant challenges to the design and configuration of a transmission assembly as it must receive the eccentric rotation of a conventional mud motor rotor, and translate that rotation to a concentric, or single axis, rotation, as may be used most easily to rotate a drill bit or other cutting implement. Transmission assemblies typically use a driveshaft with a sufficient degree of strength and flexibility to follow an orbital path proximate the coupling to the rotor of the mud motor, but to rotate relative to a single axis at a second end proximate a bearing assembly which serves, in part, to secure the single axis of rotation proximate the second end of the driveshaft.
The design and configuration of the motor transmission assembly are further complicated where mud motors will be used in potentially high stress applications, which can include motors with high force output, motors used in deep wells with potentially heavy loading on the drill bit, etc. These conditions can place exceptional strain on all components in the system, including the mud motor and associated transmission assembly. Practical issues of assembly/disassembly, transport, and repair of components in the downhole motor transmission assembly require the use of multiple components to form the drivetrain of the transmission assembly. The configuration and capabilities of the coupling connections used to connect the components forming the transmission drivetrain become of significant importance in forming a mud motor assembly with the capability of handling these extreme conditions: and new methods and apparatus for forming a motor transmission assembly are the subject of this application.